Piston



Jan. 12, 1937. NELSON 2,067,278

PISTON Filed May 28, 1935 4 Sheets-Sheet l INVENTOR: We?

MIL)

TTORNEY Jan. 12, 1937..

A. L. NELSON PISTON Filed May 28, 1955 4 Sheets-Sheet 2 10 i HQ 10 ii122 ii mu m 116 14 :96 I INZIZNTORI BY I max

A TORNEY Jan. 12, 1937. E QN 2,067,278

PISTON Filed May 28, 1935 4 shee ts sheet 3 0 INVENTOR:

A ORNEY Jan. 12, 1937. NELSON 2,067,278

PISTON Filed May 28, 1955 4 Sheets-Sheet 4 Patented Jan. 12, 1937 PATENTOFFICE 11 Claims.

This invention relates to pistons, especially to pistons for use ininternal combustion engines.

A particular object of the invention is to provide balancing ribs on thelower inner wall of the tion as hereinafter set forth and claimed.

In the drawings:

Fig. 1 is a side elevation of a piston embodying the invention;

Fig. 2 is a plan view of the lower end of the piston looking toward thehead;

Fig. 3 is a sectional view on line 3--3 of Fig. 1;

Fig. 4 is a sectional view on line 4-4 of Fig; 3;

Fig. 5 is a view similar to Fig. 4, of a modification;

Fig. 6 is a sectional view on line 6-6 of Fig. 5;

Fig. 7 is a view similar to Fig. 4, but showing a modification;

Figs. 8 and 9 are views similar to Figs. 4 and 2 of a furthermodification.

The piston illustrated in the drawings is in general the type of pistondescribed in my Patent No. 1,982,396. This piston includes piston pin.

bosses i0, opposite thrust faces ll, I2, and an annular part it belowthe pin bosses, which is reinforced by arcuate segmental ribs It coveredby my Patent No. 1,830,172. The present invention relates particularlyto the toothed ribs l5 located between the piston pin' bosses and theribs iii.

Each rib i5 extends along the inner surface of the annular part i3 belowa pin boss, and the ends of these ribs are spaced from each other behindthe thrust faces in order to permit casting the piston in a permanentmold with a threepiece core, as fully explained in Patent No. 1,830,172.For this purpose the inner skirt wall in the vertical zone in the centerof each thrust face is free of any inwardlyextending ribs or projectionsover a. considerable are, as will be clear from Figs. 2 and 3.

Each of the ribsi5 is cut through by one or more slots I6 which dividethe rib into a plurality of separate, segmental portions. The slots l6cut practically through the entire thickness of the rib so that outsideof each slot the skirt wall has substantially its normal thickness, thuspermitting the skirt to bend circumferentially at these points as freelyas though the ribs i5 were not present. This free yielding of the ribsi5 is of particular importance in a strut-controlled piston of the typeillustrated, as the struts tie rigidly together the parts of the skirtto which they are attached. It is obvious that the depth of the slotscan be varied to alter the stiffness of the ribs.

The slots I6 are substantially parallel to the axis of the piston pinbosses, as illustrated, so as to permit casting the piston with athree-piece core. This arrangement of the slots permits moving the sidecores toward the center of the piston in directions parallel to the axisof the pin bosses.

The ribs I5 are for the purpose of providing surplus material that canbe machined away to bring the piston to a certain weight in order tobalance it with others of a'set. This is usually done by machining away'part of the-inner periphery of the ribs. The division of the ribs intoseparate tooth-like portions prevents distortion of first machined to anoversize, leaving say 10 grams of material to be removed in the finalmachining. Then if the final weight of the finished piston is to be 350grams, metal is removed from the balancing ribs until the piston weighs-360 grams. The piston is last given the finish grinding which removesthe extra 10 grams from the exterior surface. If the balancing ribs werecast solid, the act of cutting away part of these ribs to balance thepiston weakens the ribs and releases certain casting strains that wereheld incheck by the relatively stiff ribs during the preliminarymachining of the piston, thus throwing the skirt out of round, twistingthe pin bosses out of line, putting the ring grooves out of true, etc.

Another advantage of this construction is that the skirt remains ofpractically the same stifiness regardless of the amount of materialremoved from the ribs in balancing the piston. If the ribs were castsolid there would be a great difierence in the skirt stifiness, rangingfrom the full stiffening effect when the rib is left intact to theentire absence of the stiffening effect of the rib if the rib isentirely cut away. v

The toothed balancing ribs i5 can be used on any desired type of piston,and they can be 10- cated at any suitable position on the inside of theskirt. Figs. 5 and 6 show a modification in which the ribs l5 arelocated on the inner walls of the thrust faces in the horizontal zone ofthe piston pin bosses.

The reinforcing ribs It may be dispensed with, or they may be placedabove the toothed ribs, as shown in Fig. 'I, which illustrates theapplication of the ribs to a piston of the all-aluminum trunk type.

In some forms of the invention the reinforcing ribs l4 may be attachedto the toothed ribs l5, as shown in Figs. 8 and 9. In this case as muchas necessary of the toothed balancing ribs Hi can be machined out, butthe machining is never permitted to cut into the ribs Hi. Thus the ribs:It always provide definite minimum stifiness in the skirt even after allof the balancing ribs l5 have been cut away.

The present application is in part a continuation of my co-pendingapplication Serial No. 631,968, filed September 7, 1932.

I claim:

1. A piston comprising a head, a skirt connected to the head, abalancing rib extending inwardly from the wall of the skirt, thebalancing rib being formed with at least one slot extending toward theouter wall of the piston and dividing the rib'into a plurality ofseparate portions the said rib furnishing excess material and beingdesigned to be cut away to balance the piston with others of a setwithout substantially altering the strength or stifiness of the skirt.

2. A piston comprising a head, a skirt connected to the head, abalancing rib extending inwardly from the wall of the skirt, thebalancing rib being formed with a plurality of slots extending towardthe outer wall of the piston and dividing'the rib into a plurality ofseparate portions the said rib furnishing excess material and beingdesigned to be cut away to balance the piston with others of a setwithout substantially altering the strength or stiffness of the skirt.

3. A piston comprising a head, a skirt connected to the head, a pair ofarc-shaped ribs extending inwardly at the lower part of the skirt, andlocated below the pin bosses, each rib being formed with at least oneslot extending toward the outer wall 01 the piston and dividing the ribinto a plurality of separate portions the said ribs furnishing excessmaterial, and being designed to be cut away to balance the piston withothers of a set without substantially altering the strength or stiffnessof the skirt.

4. A piston comprising a head, a skirt connected to the head, a pair ofarc-shaped ribs extending inwardly at the lower part of the skirt, andlocated below the pin bosses, each rib being formed with a plurality ofslots extending toward the outer wall of the piston and dividing the ribinto a plurality of separate, tooth-like portions the said ribsfurnishing excess material, and being designed to be cut away to balancethe piston with others of a set without substantially altering thestrength or stiffness of the skirt.

5. A piston comprising a head, a skirt connected to the head and havinga lower circular portion, piston pin bosses, partly-cylindrical portionsextending upwardly from the circular portion, a pair of arc-shapedbalancing ribs, each of the balancing ribs extending along the innersurface of the lower circular portion below a pin boss, the balancinribs being spaced from each other at the inner surface of each of thepartlycylindrical portions, each balancing rib being formed with atleast one slot extending toward the outer wall of the piston anddividing the rib into a plurality of separate portions the said ribsfurnishing excess material, and being designed to be cut away to balancethe piston with .others of a set without substantially altering thestrength or stifiness of the skirt.

6. A piston comprising a head, a skirt connected to the head and havinga lower circular portion, piston pin bosses, partly-cylindrical portionsextending upwardly from the circular portion, a pair of arc-shapedbalancing ribs, each of the balancing ribs extending along the innersurface of the lower circular portion below a pin boss, the balancingribs being spaced from each other at the inner surface of each of thepartlycyiindrical portions, each balancing rib being formed withaplurality of slots extending toward the outer wall of the piston anddividing the rib into a plurality of separate, tooth-like portions thesaid ribs furnishing excess material, and being designed to be cut awayto balance the piston with others of a set without substantiallyaltering the strength or sifiness of the skirt.

7. A piston comprising a head, a skirt connected to the head, piston pinbosses, a pair of arcshaped balancing ribs extending inwardly at thelower part of the skirt, each balancing rib being formed with aplurality of slots extending toward the outer wall of the piston anddividing the rib into a plurality of separate, tooth-like portions, theslots being arranged in opposed pairs, the slots of each pair openinginwardly to-. ward each other in a direction substantially parallel tothe axis of the pin bosses to permit molding the piston with athree-piece core, the said ribs furnishing excess material and beingdesigned to be cut away to balance the piston with others of a setwithout substantially altering the strength or stiiiness of the skirt.

8. A piston comprising a head, a skirt connected to the head and havinga lower circular portion, piston pin bosses, partly-cylindrical portionsextending upwardly from the circular portion, a'

pair of arc-shaped balancing ribs, each of the balancing ribs extendingalong the inner surface ,of the lower circular portion below a pin boss,the

balancing ribs being spaced from each other at the. inner surface ofeach of the partly-cylindrical portions, each balancing rib being formedwith a plurality of slots extending toward the outer wall of the pistonand dividing the rib into a plurality of separate, tooth-like portions,the slots being arranged in opposed pairs, the slots of each pairopening inwardly toward each other in a direction substantially parallelto the axis of the pin bosses to permit molding the piston with athree-piece core, the said ribs furnishing excess material and beingdesigned to be cut away to balance the piston with others of a setwithout substantially altering the strength or stifiness of the skirt.

9. A piston comprising ahead, a skirt connected to the head havingopposite thrust faces and a lower circular portion, piston pin bosses, apair of arc-shaped balancing ribs, each of the balancing ribs beinglocated below a 'pin boss and extending along the inner surface of thelower circular portion, the balancing ribs being spacm from each otherat the inner surface of each thrust face, the inner wall in the verticalzone in the center of each thrust face being free or any inwardlyextending projections over a considerable arc, each balancing rib beingformed with a plurality of slots extending transversely of the rib anddividing the rib into a plurality of toothlike portions the slots beingarranged in opposed pairs, the slots of each pair opening inwardlytoward each other in a direction substantially parallel to the axis ofthe pin bosses to permit molding the piston with a three-piececore, thesaid ribs furnishing excess material and being designed to be cut awayto balance the piston with others of a set without substantiallyaltering the strength or stiffness of the skirt.

10. A piston comprising a head, a skirt connected to the head and havingopposite thrust faces and a lower circular portion, piston pin bosses, apair of arcuate reinforcing ribs extending inwardly from the skirt wall,and a pair of arcuate balancing ribs, each balancing rib being dividedby slots into a plurality of separate tooth-like portions, saidbalancing ribs furnishing excess material, and being designed to be cutaway to balance the piston with others of a set without substantiallyaltering the strength or stiiiness of the skirt.

11. A piston comprising a head, a skirt connected to the head and havingopposite thrust faces and a lower circular portion, piston pin bosses, apair of arcuate reinforcing ribs extending inwardly from the skirt wall,each of said reinforcing ribs being located with its intermediateportion below the opening of a piston pin boss, and an arcuate balancingrib located below each reinforcing rib, said balancing ribs beingslotted into a plurality of separate tooth-like portions and furnishingexcess material and being designed to be cut away to balance the pistonwith others of a set without substantially altering the strength orstifiness of the skirt.

ADOLPI-l'.

L. NELSON.

